Prostate Cancer Screening

The prostate is a gland that helps make semen (the fluid that contains sperm) in men. It is about the size of a walnut and surrounds the tube that carries urine away from the bladder. It grows larger with age. Three most common problems that rise are infection (prostatitis), abnormal enlargement (Benign Prostatic Hyperplasia or BPH), and cancer. Prostate cancer is a leading malignancy in men over the age of 50. Early detection of prostate cancer is important.

PSA (Prostate Specific Antigen) test and Digital Rectal Examination are two tests that allow detection of prostate cancer at early stages.

More about PSA

PSA is prostate specific and not cancer specific marker as it maybe elevated in conditions other than prostate cancer like benign conditions such as prostatitis and prostate gland hypertrophy.

PSA function is to liquefy semen and keep it watery. Most of this protein is eliminated from the body through the semen; however, small measures of this antigen enter the blood stream and can be found in the blood serum.

PSA can either be attached to another compound or may exist by itself:

Attached PSA- This is a type of PSA which is complexed or attached to the protease inhibitor, alpha –1 antichymotrypsin.

Free PSA – This PSA is free and is not complexed to any molecule.

Total PSA -This is the sum of both the attached and the free form of the PSA

Quiz on Prostate cancer

Health Animation - Prostate cancer

In a standard PSA test, total PSA is usually measured. This is done by taking a blood sample and analyzing the amount of PSA. The amount of PSA in the blood is very low, therefore specific tests, such as the monoclonal antibodies, are employed to carry out the test.

Individuals with prostate cancer tend to have low percent of free PSA compared to those with the benign disease.

Normal concentration of PSA is 0-4 nanogram/ml. This concentration can vary with age. Normally, the prostate gland enlarges in older men and this leads to the increased production of PSA.

Age-specific normal PSA levels are given below:

40 – 49 yrs - 2.5ngms/ml

50 – 59 yrs - 3.5 ngms /ml

60 – 69 yrs - 4.5ngms /ml

70 – 79 yrs - 6.5 ngms /ml

PSA levels not only rise in the case of prostate cancers but also in the case of many conditions of the prostate such as:

Benign prostatic hypertrophy (BPH)

Prostate bladder or kidney infections

Poor blood supply to the prostate

Urinary retention

PSA also increases after a prostate surgery or after exams or procedures such as biopsies, catheterization or digital rectal exam.

In many cases, PSA is also carried out to check recurrence in a person with prostate cancer. Increased levels of PSA are definitely indicative of recurrence although a single PSA test may not be sufficient to confirm it.

It may be interesting to note that the PSA levels increases much before the clinical symptoms of prostate cancer manifest themselves and hence they provide a window of opportunity to cure the cancer before it spreads to other parts of the body. They are also useful in the follow up of the patients who has been treated. Any persistent elevation is considered as recurrence of the cancer.

Sometimes PSA tests reveal small tumors that are not life threatening. However this will prompt unnecessary treatment initiation. There are also several cases of false positives reported.

Digital Rectal Examination

Is a clinical examination to look for enlargement of the gland and to know if it is benign or malignant? It is done in the clinic on the doctor’s couch with the person lying on the back or the side and the knees drawn up.

FAQs

PSA (Prostate Specific Antigen) test and Digital Rectal Examination are two tests that allow detection of prostate cancer at early stages.

1) Which specialist doctor can do prostate cancer screening?

Urologist can offer such screening.

2) Who require a PSA screening test?

The use of the PSA test along with a digital rectal exam has been approved to help detect prostate cancer in men 50 years of age or older. The two tests are used as prostate cancer screening tests. PSA test is also used to follow up patients who had been treated for prostate cancer.

Men with ‘risk factors’ for developing prostate cancer require screening:

Men of the age 50 years or older require screening.

Positive family history, i.e. if someone else in your family has/had prostate cancer.

Race: African American men have the highest rate of prostate cancer. Rates are low in Asian and Native American men

Diet: A diet higher in fat, especially animal fat, may increase the risk of prostate cancer

3) How are PSA test results reported?

Results are usually reported as nanograms of PSA per millilitre (ng/mL) of blood. There is no specific normal or abnormal PSA level but less than 4 is considered normal. Values are correlated with a number of factors. The higher a man’s PSA level, the more likely it is that prostate cancer is present. 

4) What do elevated levels mean?

Elevated levels may mean the presence of prostate cancer, benign prostate enlargement, inflammation. Infection, age, race are also factors leading to raised levels. Repeated tests (PSA levels and Digital Rectal Examination) may be recommended by your doctor if you do not have any symptoms suggestive of cancer. Suspicion of cancer may mandate a battery of investigations.

A single raised PSA level is never the basis of any treatment it should always be repeated if it is elevated to reconfirm the level before asking for a prostate biopsy.

5) Does the PSA test have limitations?

It is not yet known for certain whether the PSA test actually saves lives. Sometimes it may lead to over diagnosis further leading to unnecessary treatment.

False-positive test: The PSA level is elevated but no cancer is actually present. This means that a person may be wrongly diagnosed to have cancer when he doesn’t have it.

False-negative test: Sometimes PSA levels remain normal in spite of the presence of cancer. This might lead to failure in diagnosis the tumour.

6) What is Digital Rectal Examination (DRE) to detect prostate abnormalities?

DRE is a relatively simple procedure where the doctor studies the prostate by feeling it (palpating) with a lubricated, gloved finger inserted into the man’s rectum.

The prostate gland is divided into different zones-the transition zone, central zone and peripheral zone. The peripheral zone can be felt through the rectum if enlarged. Most prostate cancer occurs in the peripheral zone. DRE is always recommended with PSA tests in men 50 years of age or older. The procedure lasts for less than minute. Though uncomfortable, the procedure usually doesn’t cause pain. A painful examination may point to benign conditions like infection (prostatitis).

7) How often do I need a DRE?

Annual check-ups are usually recommended. Please see question number 2 for further details.

8) Does a DRE always detect prostate abnormalities?

Need not. Not all parts of the prostate gland are palpable during DRE. Hence the DRE is performed best in conjunction with PSA testing.

9) What other methods are available to detect prostate cancer?

Researchers are investigating several other ways to detect prostate cancer. These include: MicroRNA patterns, Non-mutation gene alterations, Gene fusions, PCA3, Differential detection of metabolites, Proteo-imaging, Protein patterns in the blood.

Explanations of these headings are beyond the scope of this article.